Alterations in 90-day morbidity, mortality, and readmission rates following spine surgery in Medicare Accountable Care Organizations (2009-2014).

BACKGROUND CONTEXT

The impact of Accountable Care Organizations (ACOs) on healthcare quality and outcomes, including morbidity, mortality, and readmissions, has not been substantially investigated, especially following spine surgery.

PURPOSE

To evaluate the impact of ACO formation on postoperative outcomes in the 90-day period following spine surgery.

STUDY DESIGN

Retrospective review of national Medicare claims data (2009-2014).

PATIENT SAMPLE

Patients who underwent one of four lumbar spine surgical procedures in an ACO or non-ACO.

OUTCOME MEASURES

The development of in-hospital mortality, complications or hospital readmission within 90 days of the surgical procedure.

METHODS

The primary outcome measures included postsurgical complications and readmissions at 90 days following surgery. In-hospital mortality and 30-day outcomes were considered secondarily. The primary predictor variable consisted of ACO enrollment designation. Multivariable logistic regression analysis was utilized to adjust for confounders and determine the independent effect of ACO enrollment on postsurgical outcomes. The multivariable model included a propensity score adjustment that accounted for factors associated with the preferential enrollment of patients in ACOs, namely, sociodemographic characteristics, medical co-morbidities, hospital teaching status, bed size, and location.

RESULTS

In all, there were 344,813 patients identified for inclusion in this analysis with 97% (n = 332,890) treated in non-ACOs and 3% (n = 11,923) in an ACO. Although modest changes were apparent across both ACOs and non-ACOs over the time-period studied, improvements were slightly more dramatic in non-ACOs leading to statistically significant differences in both 90-day complications and readmissions. Specifically, in the period 2012-2014, ACOs demonstrated an 18% increase in the odds of 90-day complications and a 14% elevation in the odds of 90-day readmissions when compared to non-ACOs. There was no difference in hospital mortality between ACOs and non-ACOs.

CONCLUSIONS

Our study of Medicare data from 2009 to 2014 failed to demonstrate superior reductions in postoperative morbidity, mortality, and readmissions for beneficiaries treated in ACOs as compared to non-ACOs. These results indicate that meaningful changes in postoperative outcomes should not be anticipated based on organizational participation in ACOs at present.

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